Patent Application US 2014/0291065 A1 discloses a loudspeaker having an external extension that includes an enclosure, at least one speaker, and a port formed in a surface of the enclosure so as to communicate with a hollow extension extending from the port outwardly. The configuration of this loudspeaker is designed to reproduce low range frequencies only, damping or lowering both middle and high frequencies. In other words, this patent application is aimed to damp intermediate and high frequencies in order to emphasize low frequencies only.
U.S. Pat. No. 8,457,341 B2 discloses a sound reproduction system, in the form of a horn, having one or more drivers coupled to a sound barrier. Different frequency responses are obtained by altering areas and lengths of the system. As disclosed, the configuration of this patent is designed to reproduce, for example, only low frequencies, damping or lowering both middle and high frequencies.
U.S. Pat. No. 8,194,905 B1 discloses an apparatus comprising a high frequency horn placed within a low frequency horn, so that the emitted sounds are time aligned, and the sounds overlapping at the same frequencies do not cancel or cause significant interference or sound distortion. This technique uses two or more speakers.
Prior art traditional loudspeakers are basically made up of three main elements or parts.
1.-Dynamic speaker(s);
2.-Frequency dividers or crossover filters;
3.-Loudspeaker enclosures.
The dynamic speaker is an electroacoustic transducer, as its function is to transform electrical energy from an audio amplifier into acoustic energy perceivable by the human ear. Usually, said prior art technique uses three speakers in order to cover all of the frequencies that the human ear is able to hear. A low-frequency reproducing speaker (bass), middle-frequency reproducing speaker (mids), and high-frequency reproducing speaker (highs). These three speakers cover together, in theory, all of the frequencies that the human ear is able to hear, namely from about 20 Hertz up to 20,000 Hertz. In some cases, said technique uses more than one speaker for each “pathway”. This means that in said technique there are loudspeakers with two or more low-frequency reproducing speakers (bass), two or more middle-frequency reproducing speakers (mids), and two or more high-frequency reproducing speakers (highs).
Given that the signals from an audio amplifier contain all of the audible frequencies (20 Hertz to 20,000 Hertz), it is necessary to separate, in a certain way, the frequencies that each of the speakers are able to reproduce.
In order to achieve this, said technique uses frequency dividers or crossover filters. This means that in the entrance of the frequency dividers we have the signal from the audio amplifier, and in the exit of the frequency divider we have three outputs. This makes possible that the low-frequency reproducing speaker (bass) only receives low frequencies (first output), that the middle-frequency reproducing speaker (mids) only receives middle frequencies (second output), and finally, that the high-frequency reproducing speaker (highs) only receives high frequencies (third output). There are well known techniques for designing these kinds of frequency dividers based on the characteristics of the speakers used.
Lastly, said technique uses different kinds of enclosures to accommodate therein the three speakers or more, along with the frequency dividers. Below, two traditional basic forms of constructing loudspeaker enclosures using said technique are mentioned.
Hermetically Sealed Loudspeaker Enclosure
A completely-sealed, rectangular enclosure made from pressed sawdust “MDF” accommodating speakers and frequency dividers.
Bass-Reflex Enclosure Having a Vent
Enclosure containing one or more vents generally located in the front surface thereof. Said loudspeaker enclosures are made from pressed sawdust “MDF”. The vent(s) can be simply a port in the front cover of the enclosure or can be made with one or more plastic ducts, with specific length and diameter. This vent makes possible to tune the loudspeaker enclosure to the natural resonance frequency of the low-frequency reproducing speaker. This tuning is achieving by using Helmholtz resonance. By tuning the loudspeaker enclosure atresonance frequency of the low-frequency reproducing speaker (bass), the loudness of the bass response is emphasized just for that resonance frequency.
In said technique, usually the two types of loudspeaker enclosures are filled inside with an acoustic absorbent material. Typically fiberglass wool to avoid to some extent, the undesirable wave reflections produced inside thereof.
The fact that speakers of said technique are not sufficiently efficient to reproduce by themselves all of the frequencies that we can hear, forces to modify the original signal from the audio amplifier. This is because the original signal from the audio amplifier has to be divided or separated in three signals of different frequency in order to lead these signals to each of the speakers. The original signal from the audio amplifier is not the same anymore; low range frequency, middle range frequency and high range frequency are taken out from the original signal to send them all afterwards to each speaker. This separation has to be done by using frequency dividers or crossover filters.
When a frequency divider is interposed between the original signal from the audio amplifier and the speakers, various problems affecting the final reproduction of the sound emitted by the speakers of the system as a whole are presented.
Frequency dividers or crossover filters have inevitably electrical energy losses. So, from the total energy of the original signal from the audio amplifier entering them, only a portion will eventually reach the speakers
Moreover, the elements used in frequency divider such as coils, electrical resistances and capacitors modify the original signal introducing “electric noise” or current and voltage distortion in the form of harmonics. The original signal from the audio amplifier now has harmful elements that not presented before at the crossover filter output.
In other words, passive electrical elements used to separate or divide the original signal from the output amplifier into three different frequency ranges, damage and draw energy from the original signal.
Another disadvantage of frequency dividers used in said technique is that they produce the well-known “phase” distortion. This distortion is due to the time delay existing between the input signal to the frequency divider and the output signal therefrom, that will reach the speakers certain time later. This “phase” distortion produced by frequency dividers in the prior art affects the final audible quality of loudspeakers.
Another disadvantage of said technique is related with what occurs inside loudspeaker enclosures, either sealed or with vent, when the speakers are working. The low-frequency reproducing speaker (bass) generates significant air compressions and depressions inside the acoustic loudspeaker enclosures when the cones thereof move. They behave similar to a piston. The compression and depression generated inside the loudspeaker enclosure reaches the cones of the other speakers of the system, in opposite “phase”, restricting its correct operation, mainly the operation of the middle-frequency reproducing speaker. Namely, when the electrical signal from the frequency divider makes the low-frequency speaker cone move forward, depression or vacuum is generated inside the loudspeaker enclosure. Said depression inside the loudspeaker enclosure “pulls” backward the middle-frequency speaker cone, but in that moment, the middle-frequency speaker also receives an electrical signal from the frequency divider, which tries to move it forward. Similarly, when the electrical signal from the frequency divider makes the low-frequency speaker cone move backward, a pressure inside the loudspeaker enclosure is generated, said pressure “pushes” forward the middle-range speaker cone, but in this moment, the middle-frequency speaker also receives an electrical signal from the frequency divider which tries to move it backward, so there are opposite forces in the cones of the low-frequency speaker and middle-frequency speaker, caused by this operation form. These opposite speaker cone forces diminish significantly the total system efficiency that finally results in a significant acoustic distortion and therefore, in a poor audible quality.
Therefore, an object of the present invention is to provide an acoustic resonator having a single high-efficiency, full range speaker, which can reproduce with high definition almost all of the sound frequencies that humans are able to hear, unlike the three or more speakers used by the prior art. Additionally, the frequency divider filters used in the prior art are eliminated. The rectangular loudspeaker enclosures made from pressed “MDF” wood, which house speakers in the prior art are also eliminated.